CN112710647A

CN112710647A - Optical fiber Raman probe for water pollution detection

Info

Publication number: CN112710647A
Application number: CN202011411630.XA
Authority: CN
Inventors: 祝连庆; 夏嘉斌; 于明鑫; 董明利; 孙广开; 何彦霖; 庄炜
Original assignee: Beijing Information Science and Technology University
Current assignee: Beijing Information Science and Technology University
Priority date: 2020-12-03
Filing date: 2020-12-03
Publication date: 2021-04-27
Anticipated expiration: 2040-12-03
Also published as: CN112710647B

Abstract

The invention relates to an optical fiber Raman probe for detecting water pollution, which mainly comprises an excitation optical fiber, a collection optical fiber, a focusing lens and a Raman enhancement substrate reflecting mirror. The exciting light excites the optical fiber through the probe to excite the water solution on the Raman enhancement substrate reflecting mirror, and the excited Raman information is collected by the collecting optical fiber and sent to the Raman spectrometer for analysis. At the front end of the probe, a focusing lens is designed to improve excitation and collection efficiency, a filter set is added, and the signal-to-noise ratio of Raman spectrum signals is reduced. The probe greatly improves the Raman spectrum of the material index in the water pollution mainly through the design of a Raman enhanced substrate reflector, and realizes the qualitative and quantitative analysis of the Raman spectrum.

Description

Optical fiber Raman probe for water pollution detection

Technical Field

The invention relates to an optical fiber Raman probe, in particular to an optical fiber Raman probe for detecting water pollution.

Background

With the development of modern industry and society in all aspects, high-quality water resources which human beings rely on to live become more and more rare and precious, which is mainly the result that the problem of water pollution is increasingly serious and the normal utilization of the water resources is increasingly threatened. Therefore, the prevention and treatment of water pollution has become a big thing for improving and saving the living environment of human beings, and is also a real problem which is closely related to the daily life of people and directly influences the quality and the physical health of people. The water pollution source mainly relates to the following aspects:

(1) industrial emission pollution: the method comprises the industries of chemical industry, pharmacy, coking, petrifaction, printing and dyeing, papermaking, emerging cosmetic manufacturing and the like, and organic components in the wastewater comprise benzene pollutants, phenols and chlorobenzene pollutants.

(2) Drinking water pollution: in the project, pollution sources which possibly threaten human health or body functions in drinking water are mainly considered, and the key points include organic pollutants which are difficult to detect conventionally, such as carcinogenesis, teratogenicity and endocrine disruptors, and the like, involved in the existing water pollution prevention and treatment process.

(3) Domestic sewage discharge: mainly refers to daily chemical substance pollution and sewage such as excrement and urine.

(4) And (3) medical pollution discharge: the sewage discharged by medical units may carry pollutants such as medicines, infectious viruses and the like.

(5) Agricultural pollution discharge: the method mainly considers possible pollutants such as chemical fertilizers, pesticides, excrement and the like.

(6) And (3) natural pollution: the evolution of the natural environment, natural precipitation, rivers, atmospheric flows, etc. also contribute to the movement and formation of pollution. The water pollutants mainly exist in organic compounds such as carbohydrates, phosphorus compounds, nitrogen compounds, chlorides, sulfides compounds, oils and proteins.

In fact, emission standards vary, taking into account the different pollutants of each industry. After being discharged, the industrial sewage is mixed with domestic sewage and enters a sewage treatment plant for treatment, and the components and the content are extremely complex. The method for treating the organic pollutants by the sewage treatment plant mainly aims at adding a strong oxidant according to the total content of the organic matters. At the present stage, the emission indexes of the sewage treatment plant only examine whether the total emission amount of the organic pollutants reaches the standard or not, and the emission content of specific pollutants is not detected. Although the total amount of the organic pollutants in the treated sewage reaches the discharge standard, persistent organic pollutants may not be effectively decomposed and even be discharged at the content close to the original content. Therefore, a small amount or trace amount of pollutants which are high in toxicity and difficult to degrade are discharged to the natural environment, and after the pollutants are continuously accumulated, the content of the pollutants in the natural environment of a certain area is increased. This places higher and more stringent requirements on real-time, continuous monitoring of environmental pollution.

The first choice for sewage treatment is a biodegradation method, i.e. macromolecular pollutants of carbohydrate, protein, amino acid, nitrogen, sulfur and other elements are decomposed and degraded into biodegradable micromolecular components containing the same elements, and resources or energy products such as hydrogen, methane and the like which can be reused are hopefully generated, or harmless substances such as water, nitrogen and the like are generated, and greenhouse gases such as carbon dioxide and the like, harmful substances such as benzene, aldehydes, chlorine, sulfur and the like are avoided.

Timely and accurate detection and monitoring of water pollution are the primary and key links of water pollution prevention and treatment. The existing detection technologies mainly include widely applied industrial technologies such as COD (chemical oxygen demand), BOD (biochemical oxygen demand), and the like, biological item detection technologies for biological cells and infectious agents, and conventional detection technologies such as chromatography and mass spectrometry after chemical separation in laboratories (for phenols, trichloro-pentachloride compounds, carcinogens, and the like in sewage). The detection technologies involve expensive instruments, complex operation, complex detection steps and long period, and particularly in trace detection, multi-stage detection is often needed, gas/liquid chromatography and mass spectrometry are sometimes needed to be combined, and on-site and real-time monitoring is difficult to realize. In addition, some compounds can only be detected qualitatively but not quantitatively, and particularly for sewage samples, the method which can be used in drinking water cannot be used due to the reasons of large background noise, much interference and the like in sewage.

Raman spectroscopy has the ability to provide specific information on various chemical and morphological components not otherwise available, and therefore raman spectroscopic material detection capabilities have been determined. The design of fiber optic probes has advanced significantly over the past decade, suggesting that raman spectroscopy is a potential and useful clinical technique. Currently, there are some probes available commercially, but since the excitation wavelength and optical structure used are not optimized for application in water contamination detection, most of them are limited to high concentration solution detection.

The Raman spectrum is a scattering spectrum, the Raman effect is weak, and the time for exciting light to enter the aqueous solution is relatively short due to the real-time detection requirement, so that the obtained Raman spectrum effect is weaker. It is therefore desirable to employ surface enhanced raman techniques (SERS) to increase the signal-to-noise ratio of raman spectra. The characteristic pollutant molecules are identified by utilizing the comparative representation of various parameters such as characteristic fluorescence emission spectrum, characteristic absorption peak, characteristic spectrum corresponding to chemical bond or functional group and the like of the pollutant fingerprint molecules, but the surface enhancement technology is not applied to the probe manufacture in the existing optical fiber probe, so that the collection efficiency of the probe is low.

Therefore, it is necessary to design a fiber-optic raman probe for low concentration detection of water contamination that incorporates surface-enhanced raman technology.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide an optical fiber Raman probe for detecting water pollution, so that the applicability of the device is improved.

In order to solve the technical problems, the invention adopts the technical scheme that: an optical fiber Raman probe for detecting water pollution comprises a probe protective sleeve, wherein a Raman enhanced substrate reflecting mirror, a spherical focusing lens and an optical fiber bundle are arranged in the probe protective sleeve from top to bottom; the Raman enhancement substrate reflecting mirror comprises a cylindrical lens and an inclined reflecting mirror, and gold nanoparticles are uniformly arranged on the surface of the inclined reflecting mirror; the optical fiber group comprises collecting optical fibers and exciting optical fibers, the outer walls of the exciting optical fibers are uniformly wrapped with the collecting optical fibers, and the outer walls of the collecting optical fibers are wrapped with optical fiber bundle protective sleeves.

Preferably, the excitation fiber is a multimode pure quartz fiber, and the diameter of the core is 50/62.6/100 um; the collection optical fiber is a multimode pure quartz optical fiber, and the diameter of the core is 50/62.6/100 um.

Preferably, six collection optical fibers are arranged, and the six collection optical fibers are uniformly distributed around the excitation optical fiber.

Preferably, the oblique mirror is inclined at 45 ° to the probe end face.

Preferably, the probe protective sleeve is made of an aluminum sheet.

Preferably, the optical fiber bundle protective sleeve material is a polymer.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention combines the surface enhancement technology and the fiber Raman technology, improves the signal-to-noise ratio of Raman spectrum, and more efficiently detects the water pollution with low concentration;

2. the Raman probe with the surface enhancement effect has the characteristics of simple structure, convenient operation, high sensitivity and high reliability, and overcomes the defects that the conventional Raman probe has weak Raman effect, low signal-to-noise ratio and can not extract effective information with high sensitivity and high precision.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

Drawings

Further objects, features and advantages of the present invention will become apparent from the following description of embodiments of the invention, with reference to the accompanying drawings, in which:

fig. 1 schematically shows a schematic view of a fiber raman probe of the present invention.

In the figure:

1. cylindrical lens 2, oblique mirror

3. Spherical focusing lens 4 and probe protective sleeve

5. Collecting optical fiber 6 and exciting optical fiber

7. Optical fiber bundle protective sleeve

Detailed Description

The objects and functions of the present invention and methods for accomplishing the same will be apparent by reference to the exemplary embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below; it can be implemented in different forms. The nature of the description is merely to assist those skilled in the relevant art in a comprehensive understanding of the specific details of the invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar parts, or the same or similar steps.

Aiming at the defects in the prior art, the invention aims to provide a Raman spectrum measuring probe which can enter liquid to detect low-concentration water pollution in real time. The surface enhancement technology and the optical fiber Raman technology are combined, the signal-to-noise ratio of the Raman spectrum is improved, and the low-concentration water pollution is detected more efficiently. The Raman probe with the surface enhancement effect has the characteristics of simple structure, convenience in operation, high sensitivity and high reliability, and overcomes the defects that the conventional Raman probe is weak in Raman effect, low in signal-to-noise ratio and incapable of extracting effective information with high sensitivity and high precision.

In order to achieve the purpose, the Raman probe is designed with the following design goals that a Raman enhancement substrate reflecting mirror is designed at the front end of the probe, the angle of the reflecting mirror is set to be 45 degrees, gold nanoparticles are uniformly distributed on the reflecting mirror, the surface enhancement effect of Raman spectrum is ensured, and the Raman spectrum signal is greatly improved; the fiber probe excitation light and the collection light focus are ensured to be positioned on the surface of the reflector, and the Raman spectrum information of low-concentration substances in water pollution is excited and collected to the maximum extent and is used for qualitative and quantitative analysis.

The invention consists of the following parts as shown in figure 1: the surface of the inclined reflector 2, the spherical focusing lens 3, the probe protective sleeve 4, the collecting optical fiber 5, the excitation optical fiber 6 and the optical fiber bundle protective sleeve 7.

The main principle and the using method of the probe are as follows: a Raman enhanced substrate radioactive mirror is used in the probe structure, the key structure is the surface of an inclined reflecting mirror 2 with gold nanoparticles, and the signal-to-noise ratio of a Raman spectrum is greatly improved through the surface enhancement effect of the Raman spectrum. In the using process, the laser emits laser through the excitation optical fiber 6, the laser is concentrated on the reflector Surface 2 with the gold nanoparticles through the spherical focusing lens 3, the Surface of the inclined reflector 2 with the gold nanoparticles is in contact with liquid with pollutants, local electromagnetic field enhancement caused by Surface Plasma Resonance (SPR) is generated through the Surface enhanced Raman effect, the Raman spectrum signals of the pollutants in the liquid to be detected are increased, the signals are reflected through the Raman enhancement substrate reflector, penetrate through the spherical focusing lens 3 and enter the collection optical fiber 5, and the collection optical fiber 5 is formed by combining 6 optical fibers and is uniformly distributed around the excitation optical fiber.

In the fiber Raman probe structure, the Raman enhancement substrate reflector consists of a cylindrical lens 1 and an inclined reflector 2, the inclined angle of the inclined reflector 2 relative to the end surface of the probe is 45 degrees, a certain number of gold nanoparticles are uniformly designed on the surface of the inclined reflector 2 with the gold nanoparticles, and the reflection efficiency of the reflector and the Raman signal enhancement effect are ensured.

The spherical focusing lens 3 is used for focusing exciting light and collecting light, and the focus is focused on the surface of the inclined reflector 2 with the gold nanoparticles, so that the signal-to-noise ratio of a Raman spectrum, the excitation efficiency of the exciting light and the collection efficiency of a collection optical fiber are improved.

The probe protective sleeve 4 is made of an aluminum sheet, so that Raman spectrum is prevented from being generated, the probe protective sleeve is used for connecting the Raman enhanced substrate reflector and the optical fiber group protective sleeve 7, and the Raman enhanced substrate reflector and the optical fiber group protective sleeve 7 are integrated through gluing and welding, so that the strength of the optical fiber probe is improved.

The optical fiber Raman probe collecting optical fiber 5 adopts multimode pure quartz optical fiber to reduce the generation of optical fiber Raman spectrum, the diameter of the fiber core is 50/62.6/100um, a series of collecting optical fibers are designed, the application requirement and the equipped Raman spectrometer are selected as the reference, and the collecting optical fibers are designed into optical fiber bundles arranged in a single row to adapt to the slit form of the equipped Raman spectrometer and improve the Raman light collecting efficiency.

The excitation optical fiber 6 in the invention adopts multimode pure quartz optical fiber, reduces the generation of optical fiber Raman spectrum, has the core diameter of 50/62.6/100um, and designs a series of excitation optical fibers to meet different application requirements.

The optical fiber bundle protective sleeve 7 is made of polymer materials and used for fixing the probe optical fiber bundle and is connected with the probe protective sleeve 4, and the flexibility of the probe can be improved by adopting the polymer materials so as to be suitable for Raman spectrum detection of different application scenes.

The invention has the beneficial effects that: the invention combines the surface enhancement technology and the fiber Raman technology, improves the signal-to-noise ratio of Raman spectrum, and more efficiently detects the water pollution with low concentration; the Raman probe with the surface enhancement effect has the characteristics of simple structure, convenient operation, high sensitivity and high reliability, and overcomes the defects that the conventional Raman probe has weak Raman effect, low signal-to-noise ratio and can not extract effective information with high sensitivity and high precision.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims

1. A fiber optic raman probe for water contamination detection, comprising: the Raman enhanced substrate reflecting mirror, the spherical focusing lens and the optical fiber bundle are arranged in the probe protective sleeve from top to bottom;

the Raman enhancement substrate reflecting mirror comprises a cylindrical lens and an inclined reflecting mirror, and gold nanoparticles are uniformly arranged on the surface of the inclined reflecting mirror;

the optical fiber group comprises collecting optical fibers and exciting optical fibers, the outer walls of the exciting optical fibers are uniformly wrapped with the collecting optical fibers, and the outer walls of the collecting optical fibers are wrapped with optical fiber bundle protective sleeves.

2. The fiber raman probe of claim 1, wherein the excitation fiber is a multimode pure silica fiber having a core diameter of 50/62.6/100 um; the collection optical fiber is a multimode pure quartz optical fiber, and the diameter of the core is 50/62.6/100 um.

3. The fiber raman probe of claim 2, wherein there are six collection fibers arranged evenly around the excitation fiber.

4. The fiber raman probe of claim 1, wherein the oblique mirror is tilted at 45 ° with respect to the probe end face.

5. The fiber raman probe of claim 1, wherein the probe protective sheath material is aluminum sheet.

6. The fiber raman probe of claim 1, wherein the fiber bundle protective jacket material is a polymer.